Typically, a solid oxide fuel cell (SOFC) employs an electrolyte of ion-conductive solid oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly. The electrolyte electrode assembly is interposed between separators (bipolar plates). In use, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
In the fuel cell, a fuel gas channel for supplying a fuel gas such as a hydrogen-gas to the anode and an oxygen-containing gas channel for supplying an oxygen-containing gas such as the air to the cathode are formed along surfaces of the separators.
For example, in a flat stack fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2006-120589, as shown in FIG. 21, a separator 1 stacked on a power generation cell (not shown) is provided. The separator 1 is formed by connecting left and right manifold parts 2a, 2a and a part 2b at the center where the power generation cell is provided, by joint parts 2c, 2c. The joint parts 2c have elasticity.
The manifold parts 2a, 2a have gas holes 3, 4. One gas hole 3 is connected to a fuel gas channel 3a, and the other gas hole 4 is connected to an oxygen-containing gas channel 4a. The fuel gas channel 3a and the oxygen-containing gas channel 4a partially extend in a spiral pattern in the part 2b, and are opened to a fuel electrode current collector and an air electrode current collector, which are not shown, respectively, at positions near the center of the part 2b. 
The separator 1 and the power generation cell are stacked together to form stack structure. Normally, the stack is provided in a casing formed as a separate body. Therefore, the number of components is relatively large. Assembling performance is low, and the production cost is high. Since the stack is covered with the casing as the separate body, it is difficult to maintain the temperature of the stack desirably, and for example, dedicated heat insulating structure needs to be adopted. Thus, the cost for such structure is high, and the overall size of the equipment becomes large.
In the fuel cell stack, it is necessary to detect whether the fuel cells have the desired power generation performance. It is because, if the power generation performance of any of the fuel cells is lowered, the control based on the voltage of the fuel cell having the poor performance (lowest fuel cell voltage) needs to be implemented. For this purpose, normally, a cell voltage terminal provided in the separator is connected to a voltage detection apparatus (cell voltage monitor), and operation of detecting the cell voltage for each fuel cell during power generation is performed.
For example, in a fuel cell stack disclosed in Japanese Laid-Open Patent Publication No. 11-339828, as shown in FIG. 22, a plurality of cells 6 are stacked between end plates 5a, 5b. The cells 6 are joined to L-shaped voltage measurement terminals 7 integrally with the separator (the voltage measurement terminals 7 may be provided as separate bodies which are not integral with the separators). The voltage measurement terminals 7 are connected to a voltmeter (not shown) through a wiring. The components between the end plates 5a, 5b are tightened together in a stacking direction by support plates 8 fixed to four corners.
In practice, the fuel cell stack needs to be placed in a casing considering heat insulation or the like. Therefore, the wiring connected to the voltage measurement terminals 7 needs to pass through the casing to the outside. For this purpose, the casing needs to have a wiring access hole, and the fabrication cost for making the wiring access hole is required. Further, the through hole for the wiring requires seal material and heat insulating material. Therefore, the additional cost for the seal material and the heat insulating material is required.
Further, since the voltage measurement terminals 7 and the wiring are provided between the fuel cell stack and the casing, the voltage measurement terminals 7 and the wiring are exposed to the exhaust gas from the fuel cell stack, and degraded easily. In particular, in the case where the voltage measurement terminals 7 and the wiring are used in SOFC, since the exhaust gas has a considerably high temperature, the voltage measurement terminals 7 may be deformed by the heat of the exhaust gas undesirably. Thus, the deformed voltage measurement terminals 7 contact the voltage measurement terminals 7 of the adjacent separator, and short circuiting may occur between the separators.